The multi-hop wireless network communication technology is a technology by which a radio station exchanges data with the desired radio station in a multi-hop manner via multiple radio stations installed as relay stations between the radio stations.
Particularly in recent years, the cost of wireless communication devices for wireless LAN (local area network) or the like has been reduced, and sensor network technologies, including Bluetooth, which is a short-range wireless communication standard mainly for digital devices, and ZigBee, which is a short-range wireless communication standard mainly for household electrical appliances, have been standardized. Accordingly, expectation for application of wireless technologies to the industry field has been increased, and the number of application cases has been increased.
Multi-hop wireless networks are expected to contribute to reductions in the number of monitoring/control cables when they are applied to the industry field, including social infrastructure business, such as electric power or transportation, and monitoring/control networks for the manufacturing industry, such as factory automation (FA) and process automation (PA). Further, making wired cables wireless can result in reductions in the cost of cable installation or maintenance cost for a routine check. Furthermore, use of wireless technologies allows business entities to more flexibly deal with changes in operation, such as addition of equipment or a change in the configuration of equipment.
However, application of wireless real-time communication to the industry field requires high reliability, and a failure that occurs in a wireless network must be dealt with rapidly. For example, assume that a wireless network that meets a requirement by obtaining multiple paths using multi-hop communication is constructed. In this case, when one path fails, the reliability of one path will decrease. For this reason, in the construction of a path, it is necessary to design a favorable path that is insusceptible to the other paths to the extent possible. Further, even if the propagation state is favorable when a radio station is installed, the state may significantly change as the time passes.
For these reasons, it is desirable to measure the radio wave propagation state in positions in which radio stations can be installed at the site at which a wireless network is planned to be constructed and to design the layout of the radio stations on the basis of the measurement results. However, it is difficult to make actual measurements in all parts of a wide industrial field. For this reason, instead of making measurements comprehensively as described above, it is necessary to estimate the propagation environment of the site by constructing virtual models on a computer and then performing radio wave propagation simulations. Further, when the propagation state changes as the time passes, it is necessary to identify the cause of the change.
However, performing a radio wave propagation simulation requires three-dimensional shapes of structures included in the site at which a radio network is planned to be constructed and material property information of the structures, such as permittivity, permeability, or conductivity. Further, even when the environment changes, it is necessary to be able to easily identify the causes of changes in the three-dimensional shapes and the material property information corresponding to the change in the environment.
There are also techniques which use a statistical model based on experimental values in various places to estimate radio wave propagation. However, to construct a radio network system which is required to be reliable as described above, it is desirable to design a network which considers a propagation environment specific to the site.
With regard to these points, Patent Literature 1 generates polygon data for radio wave propagation simulation using a laser scanner, image sensor, or the like. Patent Literature 1 further discloses a method of obtaining three-dimensional point coordinate group data using a laser scanner disposed in a mobile object and generating polygon model data in space along the traveling direction of the mobile object.